This common painkiller cannot ease chronic pain after injury

October 11, 2018

A common painkiller isn’t effective in controlling the chronic pain that sometimes develops following traumatic nerve injury—but shows promise in relieving pain that may linger after surgery, according to a new study.

The FDA has approved pregabalin, which Pfizer markets under the name Lyrica, to treat chronic pain associated with shingles, spinal cord injury, fibromyalgia, and diabetic peripheral neuropathy.

However, it is also commonly prescribed as an “off label” treatment for chronic nerve injury syndromes that occur after motor vehicle accidents, falls, sports injuries, knee or hip replacement, and surgeries such as hernia repair or mastectomy.

“The unrelenting burning or stabbing symptoms due to nerve trauma are a leading reason why people seek treatment for chronic pain after a fall, car accident, or surgery,” says John Markman, lead author of the study.

“While these finding show that pregabalin is not effective in controlling the long-term pain for traumatic injury, it may provide relief for patients experience post-surgical pain.”

55 MILLION SURGERIES A YEAR

A previous eight-week study had shown that pregabalin reduced pain intensity better than a placebo in these chronic, post-traumatic pain syndromes.

Those results led many doctors to prescribe the medication for long-term pain that does not resolve as expected.

Chronic postsurgical pain syndromes occur in approximately one or two out of every 10 surgical patients and leads to pain levels rated as intolerable after roughly one or two in every 100 operations.

With 55 million surgeries performed in the US every year, severe chronic pain affects more than a million new people annually.

Researchers believe roughly one third of these patients may have neuropathic pain or ongoing pain related to nerve injury.

These rates vary widely by type of surgery.

The risks factors and underlying mechanisms of this type of chronic pain are not well understood, but because the types of symptoms patients describe like “burning”, “unpleasant tingling,” or “numbness” resemble other nerve pain syndromes like shingles pain.

As a result, physicians trying to find useful non-opioid pain relievers have often turned to prescribing gabapentin or pregabalin.

Researchers conduced the current study in 101 centers in in North America, Europe, Africa, and Asia and followed 539 individuals for three months.

They randomized study participants into two groups who either received pregabalin or a placebo.

The study found that pregabalin was not effective in controlling pain for individuals with traumatic nerve injury.

A retrospective analysis of a subgroup of study of participants, whose nerve pain was attributed to surgery, showed that the drug did provide better pain relief than placebo at three months.

WHO WILL IT HELP?

“The possibility that there was pain relief for those patients who had a hernia repair, or breast surgery for cancer, or a joint replacement lays the groundwork for future studies in these postsurgical syndromes where there is so much need for non-opioid treatments,” Markman says.

One major challenge is that different biological changes in the nerves and other tissues that cause pain to persist after healing from trauma vary from one patient to the next.

Currently, there is no diagnostic method that allows doctors to readily identify the patients whose pain will respond to a particular type of pain treatment.

Despite employing new strategies to reduce placebo effects, the patients receiving placebo also had a steady lowering of their pain over the course of the study.

The pattern of these placebo effects in longer studies has proved to be a major challenge to the development of new pain medications.

“Given the rising rates of surgery and shrinking reliance on opioids, it is critical that we understand how to study new drugs that work differently in patients like the ones included in this study,” Markman says.

Additional coauthors are from Pfizer and Analgesic Solutions. Pfizer funded the trial, and was involved in its design as well as the data collection and analysis.

The company also paid for medical writing assistance and editorial support in preparing the article for the journal. Markman has received consulting fees and research funding support from Pfizer.